The present invention relates to photographic printing involving the exposure of light-sensitive materials to light passing through negatives or transparencies. Adjustment is made with respect to the density and/or color variations of the negatives or transparencies.
Negatives and transparencies can suffer from "color subject failure" in which some areas are under exposed and other areas are over exposed on the negative or transparency. Printing from such negatives or transparencies is a problem because the print will also have corresponding under exposed and over exposed areas unless steps are taken to compensate for such varying degrees of exposure.
For example, consider a negative for the sky, a lake, a wooded area and a dirt road. Assume the sky and lake are light blue and overexposed, the wooded area has a normal exposure and the dirt road is under exposed.
If a darkroom technician attempts to keep color and detail in the sky and lake in exposing a print from the negative, the dirt road will be black with no detail. If the print is exposed instead to show the detail in the road, the sky and lake will be washed out.
In practice, darkroom technicians compromise by averaging the exposure and shooting for the middle, but this method does not work very well. Burning and dodging the beam of light manually is another method used, but this method is inconsistent and dependent upon the skill of the technician in custom printing. Unfortunately, such techniques do not provide the control necessary for obtaining prints with a "near unity density coefficient" in which the print appears to have a consistent normal exposure throughout.
It would therefore be desireable to print from a negative or transparency so as to enable compensation for varying degrees of over exposure and under exposure in the negative or transparency.